JPH01150989A - Graphic display device - Google Patents

Abstract

PURPOSE:To attain a painting-out even in a polygon having a recessed part by reversing display data between two points. CONSTITUTION:Respective points on a scanning line L (y=Y) to cross the recessed part are painted out as follows. Coordinates (Xalpha, Y) of a point alphaon a side AB are calculated at a coordinate calculating part 1, and its x- coordinate value is stored in a coordinate storing part 2. While coordinates (Xbeta, Y) of a point beta on a side BC are calculated at the coordinate calculating part 1, the x-coordinate Xalpha of the point alpha is fetched from the coordinate storing part 2, the two points (Xalpha, Y) and (Xbeta, Y) and the display data of points between them are reversed, and when the initial state of a picture memory is initially set to an 'all points white', a segment alphabeta is painted out in black. Coordinates (Xgamma, Y) of a point gamma on a side CD are calculated at the coordinate calculating part 1, and its x-coordinate value is stored in the coordinate storing part 2. While coordinates (Xdelta,, Y) of a point delta on a side AD are calculated at the coordinate calculating part 1, the x-coordinate Xgamma of the point gamma is fetched from the coordinate storing part 2, and the two points (Xgamma, Y) and (Xdelta, Y) and the display data of the points between the two points are reversed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a graphic display device that fills in arbitrary polygons in image display devices such as graphic display devices and laser beam printers.

BACKGROUND ART Conventionally, the following methods have been used to fill in the interior of an arbitrary polygon.

(1) A method in which an arbitrary polygon is divided into pentagons and each pentagon is filled in.

(2) Calculate the coordinates of points (contour points) on each side of the polygon, sort the contour points on the same horizontal or vertical scanning line in order of coordinates, and draw points between adjacent contour points. A method that fills the inside of a polygon.

(3) Set the coordinates of the points (contour points) on each side of the polygon clockwise,
Alternatively, the calculation is performed in a counterclockwise direction, and if two contour points on the same horizontal or vertical scanning line appear, the interior of the polygon is filled by inverting the points between the two points (for example, ``There is Japanese Patent Application Publication No. 57-101886J).

Problems to be Solved by the Invention However, each of the above systems has the following problems.

The method (1) requires processing to divide an arbitrary polygon into convex angles, which slows down the processing speed. Furthermore, the mechanism for managing the divided convex angles becomes complicated.

The method (2) requires a large-scale storage means for storing contour points, and sorting of contour point coordinates is complicated and time-consuming.

Although the number of coordinates in method (3) is significantly smaller than that in method (2), the coordinates are stored in a table format using the y-coordinate value as an index, so the coordinate storage section is large. In addition, each time a coordinate value is stored or retrieved, the presence or absence of the coordinate value is determined, written, read,
Multiple memory accesses to the coordinate storage unit are required for operations such as deletion.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a graphic display device that can quickly fill in arbitrary polygons using simple operations and a small storage capacity.

Means for Solving the Problems In order to solve the above problems, the present invention provides a coordinate calculation unit that sequentially calculates coordinate data of points on sides of a polygon from coordinate data of vertices of the polygon; a first-in, last-out type coordinate storage unit that stores coordinate data calculated by the unit;
detecting a change in the coordinate calculation direction in the coordinate calculation unit;
Either the coordinate data calculated by the coordinate calculation section is stored in the coordinate storage section, or the coordinate data is taken out from the coordinate storage section and combined with the data calculated by the coordinate calculation section, and the data is calculated between the two points. This graphic display device includes a control section that switches whether to draw a straight line connecting the two points, and a straight line drawing section that inverts display data of a point between the two points on an image memory based on the coordinate data of the two points.

In the present invention, in any polygon, a horizontal or vertical scanning line intersects the contour of the polygon an even number of times, except for singular points at vertices, and the intersections are made into pairs of two points. Focusing on the fact that filling can be achieved even in a polygon having a concave portion by inverting the display data between two points, the following effects are realized by the above-mentioned configuration.

In the coordinate calculating section, the coordinates of points on each side of the polygon, that is, the coordinates of the intersections between each side of the polygon and each scanning line, are sequentially calculated by tracing the outline clockwise or counterclockwise. Initially, since the coordinates of other contour points on the same scanning line forming a set have not yet been calculated, the control unit stores the calculated coordinate data in the coordinate storage unit. Thereafter, when the coordinate calculation direction is reversed in the coordinate calculation section, the coordinates of another contour point on the same scanning line as the point whose coordinates were previously calculated and stored in the coordinate storage section are sequentially calculated. Note that the coordinate calculation direction referred to here refers to the direction of change in coordinates that serve as a reference when calculating coordinates. For example, if the scanning line is parallel to the X-axis, the coordinate calculation unit calculates the coordinates while increasing or decreasing the y-coordinate value by 1.

The direction in which the y-coordinate value changes at this time, that is, the positive or negative sign of the y-coordinate increment, is referred to as the coordinate calculation direction.

The direction of this coordinate calculation is from the positive direction to the negative direction, or
If the direction changes from negative to positive, the direction of coordinate calculation is said to have been reversed. Note that during the direction change, the direction of the side may pass through a scanning line direction (y coordinate increment of 0) in which the direction coincides with the direction of the scanning line. However, for points on the sides in the scanning line direction, calculated coordinate data is neither stored nor straight lines are drawn.

When the coordinate calculation direction is reversed in the coordinate calculation unit, the control unit retrieves already stored coordinate data one by one from the coordinate storage unit each time the coordinate calculation unit calculates the coordinate data of the contour point. Since the coordinate storage unit is of a first-in, last-out type, the coordinate data is retrieved in the reverse order in which it was stored. Therefore,
The coordinate data retrieved from the coordinate storage section is always of a contour point on the same scanning line as the calculated contour point.

In this way, the coordinate data of two points on the same scanning line (the newly calculated coordinate data in the coordinate calculation section and the coordinate data retrieved from the coordinate storage section) are obtained, and the straight line drawing section calculates the coordinate data for both points and the image point. Inverts the display data on the image memory at the points between.

Thereafter, the control section switches between storing the coordinate data in the coordinate storage section and retrieving the coordinate data from the coordinate storage section and drawing a straight line every time the coordinate calculation direction is reversed in the coordinate calculation section.

The above operations are performed for all of the given polygons, and when the coordinate calculation unit finishes calculating the coordinates of all points on the sides of the polygon,
A filled polygon is generated.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the graphic display device of the present invention. 1 is a coordinate calculation unit that sequentially calculates the coordinates of points on the sides of a polygon; 2 is a first-in, last-out type coordinate storage unit that stores the calculated coordinate data; and 3 is a coordinate storage unit that stores the coordinate data in the coordinate storage unit 2. Storage processing and.

A control unit that switches between retrieving coordinate data from the coordinate storage unit 2 and straight line drawing processing; 4 is a straight line drawing unit that inverts and draws display data on the image memory of a point between two specified points; 5 is a display data This is an image memory that stores images.

The operation of the graphic display device according to the embodiment of the present invention constructed as described above will be explained using the example shown in FIG.

In the following description, the horizontal direction is the X-axis direction, the vertical direction is the y-axis direction, the right direction is the X-axis stopping direction, and the upper direction is the y-axis stopping direction. Furthermore, for simplicity, the image is assumed to be a black and white binary image.

The coordinate calculation unit 1 sequentially calculates the coordinates of the intersections between each side of the polygon and the scanning line along the contour from the provided polygon vertex coordinate data 6. The contour may be traced in either a clockwise or counterclockwise direction; however, in the following explanation, an example will be taken in which coordinates are calculated while tracing the contour counterclockwise.

Therefore, coordinate calculation is side AB, side BC1 side CD, side DA
This is done in the following order. Note that the calculation method uses the well-known DDA (
Digital Differential An
alyze) algorithm is used.

First, the coordinate calculation unit 1 sequentially calculates the coordinates of points on side AB by decreasing the y coordinate by one. The control unit 3 stores the calculated coordinate data in the coordinate storage unit 2. Coordinate storage unit 2
The coordinate data stored in may be only the X coordinate value.

When the coordinate calculation unit 1 finishes calculating the coordinates of a point on side AB and moves on to calculating the coordinates of a point on side BC, it is found that although the direction of coordinate calculation on side AB is downward with the y-coordinate decreasing sequentially. On the other hand, the direction of coordinate calculation on side BC is upward with the y-coordinate increasing sequentially, and the direction of coordinate calculation is reversed. The control unit 3 detects this reversal of the coordinate calculation direction, and switches the process of storing the coordinate data in the coordinate storage unit 2 to the process of retrieving the coordinate data from the coordinate storage unit 2 and drawing a straight line. That is, each time the coordinate calculation unit 1 calculates coordinate data, it retrieves one by one the coordinate data stored in the coordinate storage unit 2 in the previous coordinate data storage process. Since the coordinate storage section 2 is of a first-in, last-out type, the coordinate data is retrieved in the reverse order of storage. Therefore, the y-coordinate value of the retrieved coordinate data changes in the opposite way to that at the time of storage. In other words, the side AB stored -
The direction in which the y coordinate changes when extracting the coordinate data of the upper point matches the coordinate calculation direction (the direction in which the y coordinate is increased by 1) on the side BC. Since point B is common to side AB and side BC, naturally the y coordinate of point B is the same, and the same −y
The y-coordinate of a point on side BC calculated by the coordinate calculation unit 1, which changes in the same direction from the coordinates, and the point on side AB taken out from the coordinate storage unit 2 every time the coordinate calculation unit 1 calculates the coordinates. The y coordinates of the coordinate data always match.

In this way, the coordinates of two points having the same -y coordinate, that is, on the same scanning line, are determined. The straight line drawing unit 4 inverts the display data on the image memory of the two determined points and the points between them. If the image memory is initially set to all white points, the inversion will turn them black.

When the coordinate data is retrieved from the coordinate storage unit 2 and the straight line drawing process is performed up to the point E on the side BC, the coordinate storage unit 2
All the coordinate data within is consumed, and the coordinate storage section 2 becomes empty. At that point, the control section 3 returns to the process of storing the coordinate data calculated by the coordinate calculation section 1 in the coordinate storage section 2 again.

From then on, the control unit 3 performs coordinate data storage processing and coordinate processing every time the coordinate calculation direction is reversed in the coordinate calculation unit 1, or whenever the coordinate storage unit 2 becomes empty during coordinate data retrieval and straight line drawing processing. Switches data retrieval and straight line drawing processing. Therefore, after point E, the coordinate calculation unit 1
While calculating the point on C, the coordinate data is stored, and the coordinate calculation unit 1 moves on to calculating the coordinate of the point on side CD, and when the direction of coordinate calculation is reversed (from upward to downward),
Shift to coordinate data extraction and straight line drawing processing.

During extraction of coordinate data of side CD and straight line drawing process,
Since the coordinate storage section 2 becomes empty again at point F, the coordinate data storage process is performed after point F until the next point where the coordinate calculation direction is reversed. When the coordinate calculation unit 1 moves to calculate the coordinates of a point on the side DA, the coordinate calculation direction is reversed again (from downward to upward), and the process moves to extraction of coordinate data and straight line drawing processing. At this time, the inside of the triangle DAF is filled in, but since the triangle DAF has already been filled in black, it returns to white by inversion.

Note that the generation of the filled polygon is completed when the coordinate calculation unit 1 finishes calculating the coordinates of all points on the polygon outline.

By the above operation, each point on the scanning line L (y=Y) that crosses the recess is filled in as follows.

(1) The coordinate calculation unit 1 calculates the coordinates (Xα, Y
) is calculated, and the X coordinate value is stored in the coordinate storage section 2.

(2) The coordinate calculation unit 1 calculates the coordinates of point β on side BC (Xβ, Y
) is calculated, and the X coordinate Xα of point α is taken out from the coordinate storage unit 2, and the two points (Xα, Y), (Xβ, Y)
and the display data of the points between them are inverted. When the initial state of the image memory is set to all black and white, the line segment αβ is filled with black.

(3) The coordinate calculation unit 1 calculates the coordinates of point γ on side CD (Xγ, Y
) is calculated, and the X coordinate value is stored in the coordinate storage section 2.

'(4) The coordinate calculation unit 1 calculates the coordinates (Xδ,
Y) is calculated, and the X of point γ is calculated from the coordinate storage unit 2.
The coordinates Xγ are extracted and the two points are Xγ, Y), (Xδ, Y
) and the display data of the points between them are inverted. That is,
In (2), since the line segment αβ including the line molecule δ is filled in black, the line molecule δ is reversed and returns to white at this time.

In the example shown in FIG. 2, the case where an arbitrary polygon is filled with horizontal line segments has been described, but it is also possible to fill it in the vertical direction.

Effects of the Invention As described above, according to the present invention, it is possible to fill any polygon at high speed with very simple processing. Furthermore, by realizing the coordinate storage unit as a first-in, last-out type memory, it can be realized with a small memory size that is at most the height of the polygon to be displayed (the length in the y-axis direction), and the coordinate storage unit can be This has the advantage that operations such as determining the presence or absence of data, reading data, and writing data can be realized at high speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a graphic display device according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the operation of the device. DESCRIPTION OF SYMBOLS 1... Coordinate calculation unit, 2... Coordinate storage unit, 3... Control unit, 4... Straight line drawing unit, 5... Image memory, 6...
...Polygon vertex coordinate data. Name of agent: Patent attorney Toshio Nakao Hakaichi Kinyo 1 Figure 2

Claims (1)

[Claims] a coordinate calculation unit that sequentially calculates coordinate data of points on the sides of the polygon from coordinate data of vertices of the polygon; and a first-in, last-out type coordinate storage unit that stores the coordinate data calculated by the coordinate calculation unit. , detecting a change in the coordinate calculation direction in the coordinate calculation section, and storing the coordinate data calculated by the coordinate calculation section in the coordinate storage section, or extracting the coordinate data from the coordinate storage section and performing the coordinate calculation. From the coordinate data of the two points,
A graphic display device comprising: a straight line drawing unit that inverts display data of a point between two points on an image memory.